1. Field of the Invention
This specification relates to a butterfly valve capable of controlling a flow of a fluid according to a rotation of a disk disposed in a valve body.
2. Background of the Invention
Generally, valves are installed at parts of a piping system formed by pipes, etc. which form a flow passage of a fluid. These valves serve to control a flow of a fluid to be stopped or to be maintained.
Among these valves, a butterfly valve is configured to open and close a pipe according to a rotation of a disk installed in a valve body. More concretely, a sealing device (sealing unit) is arranged to block a gap between an opening and closing member (disk) and a housing of the butterfly when fluid flow is in a stopped state.
The sealing unit is installed at the housing in a contacted state to the opening and closing member with an initially preset pressure. However, the sealing unit may be abraded according to lapses of time. Accordingly, a sealing degree has to be controlled. Furthermore, a closely contacted state between the sealing unit and the disk should not be loosened due to a thermal deformation occurring when a fluid has a high temperature. When a fluid has a high pressure, the closely contacted state between the sealing unit and the disk should be maintained more stably. To satisfy these conditions, a new method may be considered.